Another on openings in walking surfaces

[bill1952]

For a very long time - over a hundred years - theatres have been designed and constructed with "gridirons" over the stage. I've been on the from probably 40' to over 175' above the stage. Earlier last century the were wood with some steel, today all steel. The classic design is a walk surface of 3 or 4 inch steel channels flanges down/ web up on 6 or 7 inch centers on steel framing. The three and some 8-10 inch openings are to accommodate the equipment and parts and pieces that are necessary to pass through the floor for rigging things.

My interest is in knowing how you apply the building code to a walking surface that has long 3" wide openings. These are regulated in section 410 as Technical Production Areas. For the moment I'll ignore the 8-10" wide openings typically every 10'. I'm dealing with OSHA separately.

In the photo, the yellow is the tops or webs of 4" channels 7" on center. The rows of pulleys and lines dropping are through the 8" gaps every 10' - 9 rows on this stage. And when in use - not barely new as in photo - there would be other equipment spread around on the gridiron. A typical detail also.

 

[e hilton]

No answer but … recently i have watched a couple of youtube videos about setting up events like taylor swift concerts, and also one where the guy was in the above-stage area just like your picture. Definitely not something i would want to do.

 

[walker.t]

My interest is in knowing how you apply the building code to a walking surface that has long 3" wide openings. These are regulated in section 410 as Technical Production Areas. For

Let’s start with the definition of “technical production area”: “Open elevated areas or spaces intended for entertainment technicians to walk on and occupy for servicing and operating equipment technology systems and equipment. Galleries, including fly and lighting galleries, gridirons, catwalks, and similar areas are designed for these purposes.”

Only entertainment technicians are going to be in the area with the openings that you described. They are trained to work in that kind of environment and the risks come with the job. The typical concerns for public safety provided by the building code would not apply in this specialized (and inherently dangerous) work area.

You’ll provide the necessary means of egress as described in 410.5.3. Notice that the highest that goes is ladders, it doesn’t include whatever is above to which the ladder could be leading (which could be your gridiron.)

If you know of a theater that has recently been constructed maybe you can submit a records request to see the drawings that were approved for that project to see how they handled things.

 

[bill1952]

I have lots of construction documents for these that I've prepared are constructed, so I know how they're built. Before I designed these I worked in these places and honestly, never gave a second thought to these open areas. (Also had little training - just knew what had to be done.) And I know most of the people in US designing these. And as far as the codes, if you go through the record you'll find my name on most changes since the late 1980s. And I taught at a college a few years and routinely took students to the gridiron and other technical production areas.

So, since this issue has rarely been flagged in a review, I was curious why. I know of one in Ontario where they were required to add a lot of guardrails, (and several times someone doing a safety report notes OSHA doesn't allow openings in floors greater than 2" in the least dimension.)

Got one of those emails this month - because people contact me when they have a theatre code question - so thought I'd ask here - especially since in midst of preparing change proposals for next cycle (due in January 2025).

 

[bill1952]

Wanted to post this also.

Behind the Scenes: The Grid | Come with us to the highest part of our building! The Grid, 25 metres above the Lyric stage, is the support structure for our counterweight flying... | By Theatre Royal PlymouthFacebook

Come with us to the highest part of our building! The Grid, 25 metres above the Lyric stage, is the support structure for our counterweight flying...

www.facebook.com

 

[walker.t]

I have lots of construction documents for these that I've prepared are constructed, so I know how they're built. Before I designed these I worked in these places and honestly, never gave a second thought to these open areas. (Also had little training - just knew what had to be done.) And I know most of the people in US designing these. And as far as the codes, if you go through the record you'll find my name on most changes since the late 1980s. And I taught at a college a few years and routinely took students to the gridiron and other technical production areas.

I didn’t mean to step on your toes or imply you didn’t know what you’re doing, I hope that isn’t how my comment came across.

I have lots of construction documents for these that I've prepared are constructed, so I know how they're built.

My suggestion to investigate drawings of approved projects wasn’t to figure out details of construction but to see if they added any notes addressing the matter of the gaps in the gridiron, like, “Openings greater than X” permitted per [code reference].”

 

[bill1952]

I didn’t mean to step on your toes or imply you didn’t know what you’re doing, I hope that isn’t how my comment came across.


My suggestion to investigate drawings of approved projects wasn’t to figure out details of construction but to see if they added any notes addressing the matter of the gaps in the gridiron, like, “Openings greater than X” permitted per [code reference].”

Thank you for posting. I'd say by observation - projects I've worked on and those if others - design documents and the completed construction - that few think about this. It's a design that is very time tested. I honestly don't know of a practical alternative to this. Maybe a simple exception for stages - technical production areas - is necessary.

 

[walker.t]

Thank you for posting.

You’re welcome.

Maybe a simple exception for stages - technical production areas - is necessary.

This sounds like a very reasonable solution. The technical production areas have a relatively small area compared to the rest of the building, are not accessible to the public, are accessed by relatively few technical staff, use non-combustible construction, and the long history demonstrates that they are safe all things considered.

 

[bill1952]

You’re welcome.


This sounds like a very reasonable solution. The technical production areas have a relatively small area compared to the rest of the building, are not accessible to the public, are accessed by relatively few technical staff, use non-combustible construction, and the long history demonstrates that they are safe all things considered.

All true. In California - schools at least - they have to be accessible. And I will note I have quite a few catwalks with wood decking.

I'm mostly trying to figure out why what seems to be non-compliant with building codes is not just permitted but usually without question.

 

[walker.t]

In California - schools at least

Wow, I can’t imagine a school having something so nice, I only went to small, poor schools growing up. We had a stage but nothing overhead, they had areas to the sides of both curtains tor hiding the scene backdrops when needed.

I'm mostly trying to figure out why what seems to be non-compliant with building codes is not just permitted but usually without question.

This is a good question. I thought a little about that, I noticed that 410.2.2 says “These areas shall not be considered to be floors, stories, mezzanines or levels in applying this code.” But that probably has to do with occupant load calculations and allowable numbers of stories. And the code does specify egress requirements so they recognize that someone is going to be using the space. It’s almost like they are considered an extension of the structural frame, but there are requirements for protection of the [primary] structural frame of the building.

Maybe plans reviewers feel like they can’t comment because the code hasn’t included more detailed requirements, so without a code provision to cite they don’t have backup?

I don’t know how many injuries are reported in a year related to technical production areas but assuming that number is very low, it’s probably not a priority for ICC to address the topic. Maybe it’s the “If it’s not broke, don’t fix it” mentality? But still, a simple exception stated in the code would be helpful.

 

[bill1952]

Injuries on these areas are almost unheard of. The problem is when some leans too far or more often climbs over a catwalk guard. A number of those.

When in HS and college, I crawled over plaster on metal lath ceilings to reach lighting. I have a lot of respect for strength of plaster on metal lathe and the fitting.

More than a few times I've know inspectors not comfortable in those areas.

 

[walker.t]

I crawled over plaster on metal lath ceilings to reach lighting.

You are a brave soul!

This guy should have been crawling…

Actually, a pretty decent demonstration that your 3” wide openings are pretty safe.